Electric work machine

ABSTRACT

An excavator comprising: an electric motor having a commercial power supply and a battery as the drive power sources therefor; and a hydraulic actuator having a hydraulic pump driven by the electric motor, as the hydraulic source therefor. The excavator has: a first power supply mode in which the electric motor is driven while the battery is being charged by the commercial power supply; and a second power supply mode in which the electric motor is driven only by the battery. A power supply cable for supplying power from the commercial power supply is connected to a power supply port and, if the electric motor has stopped operating, the excavator moves from the second power supply mode to the first power supply mode.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a national stage application pursuant to 35 U.S.C. §371 of International Application No. PCT/JP2019/016570, filed on Apr.18, 2019 which claims priority under 35 U.S.C. § 119 to Japanese PatentApplication No. 2018-083100 filed on Apr. 24, 2018, the disclosures ofwhich are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to an electric work machine.

BACKGROUND ART

In Patent Literature 1 below, a construction machine on which a powersupply system for driving an electric motor with a commercial powersupply and a battery is mounted is disclosed. This power supply systemincludes a power supply switching device that switches an electricalcircuit between an electrical circuit that supplies a direct-currentpower supply from the battery to an inverter converting direct-currentpower into any alternating-current power and supplying thealternating-current power to the electric motor and an electricalcircuit that converts the alternating-current power supplied from thecommercial power supply into the direct-current power via an AC/DCconverting section and supplies the direct-current power to theinverter.

In Patent Literature 2 below, in an electric excavator having; a modefor driving an electric motor while a battery is being charged by anexternal power supply; and a mode for driving the electric motor by thebattery only, a technique of shifting to the mode for driving theelectric motor while the battery is being charged by the external powersupply by connecting the external power supply during the mode fordriving the electric motor by the battery only is disclosed.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Unexamined Patent Application    Publication No. 2007-228715-   Patent Literature 2: Japanese Unexamined Patent Application    Publication No. 2008-308881

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

In Patent Literature 1, the commercial power supply and the battery areselected. Thus, in the case where the electric motor is driven only withthe power from the commercial power supply, the power for driving theelectric motor depends on the commercial power supply, which leads tosuch a problem that sufficient drive power cannot be obtained in a caseof work requiring the high drive power. In Patent Literature 2, a powersupply cable for supplying the power from the external power supply isconnected to the machine that is being driven by the battery only. Thus,there is a risk of arc discharge. Furthermore, act of connecting thepower supply cable to the machine that is being driven by the batteryonly possibly causes an accidental contact due to turning and travelingmotion of the machine.

The present invention has been made in view of the above problems andtherefore has a purpose of providing an electric work machine capable ofinhibiting act of connecting a power supply cable from an external powersupply to the machine that is being driven and preventing arc dischargeeven when the power supply cable is connected.

Means for Solving the Problems

An electric work machine according to the present invention is anelectric work machine including: an electric motor having an externalpower supply and a battery as drive power sources; and a hydraulicactuator having, as a hydraulic pressure source, a hydraulic pump drivenby the electric motor, and

has: a first power supply mode in which the electric motor is drivenwhile the battery is being charged by the external power supply; and asecond power supply mode in which the electric motor is driven by thebattery only.

In the case where a power supply cable for supplying electric power fromthe external power supply is connected to a power supply port androtation of the electric motor is stopped, the second power supply modeis shifted to the first power supply mode.

In the present invention, in the case where the power supply cable forsupplying the electric power from the external power supply is connectedto the power supply port, where the rotation of the electric motor isstopped, and where a cut-off lever for restricting an operation of thehydraulic actuator is rotated upward by blocking a pilot pressure usedto operate the hydraulic actuator, so as to restrict the operation ofthe hydraulic actuator, the second power supply mode may be shifted tothe first power supply mode.

In the present invention, in the case where the power supply cable isdisconnected from the power supply port, the first power supply mode maybe shifted to the second power supply mode.

According to the present invention, the second power supply mode is notshifted to the first power supply mode unless the rotation of theelectric motor is stopped. Therefore, it is possible to inhibit act ofconnecting the power supply cable from the external power supply to themachine that is being driven. Even in the case where the power supplycable is connected, arc discharge does not occur.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view illustrating an electric work machine according tothis embodiment.

FIG. 2 is a side view in which a portion of the electric work machinearound a cut-off lever is enlarged.

FIG. 3 is a view illustrating a hydraulic circuit of the electric workmachine.

FIG. 4 is a block diagram of a power supply system mounted on theelectric work machine.

FIG. 5A is a block diagram of the power supply system implementing acommercial power supply mode.

FIG. 5B is a block diagram of the power supply system implementing atwo-way mode.

FIG. 5C is a block diagram of the power supply system implementing abattery mode.

FIG. 5D is a block diagram of the power supply system implementing acharging mode.

FIG. 6 is a flowchart illustrating a procedure of switching control of apower supply mode.

FIG. 7 is a flowchart illustrating a procedure of switching controlbetween the two-way mode and the battery mode.

FIG. 8 is a flowchart illustrating a procedure of the switching controlbetween the two-way mode and the battery mode according to anotherembodiment.

DESCRIPTION OF EMBODIMENTS

A description will hereinafter be made on embodiments of the presentinvention with reference to the drawings.

[Configuration of Electric Work Machine]

First, a description will be made on a schematic structure of anexcavator 1 as an example of the electric work machine with reference toFIG. 1 and FIG. 2. However, the example of the electric work machine isnot limited to the excavator 1, and may be another vehicle such as awheel loader. The excavator 1 includes a lower travel body 2, a workunit 3, and an upper turning body 4.

The lower travel body 2 includes a left and right pair of crawlers 21,21 and a left and right pair of travel motors 22L, 22R. The left andright travel motors 22L, 22R as hydraulic motors drive the left andright crawlers 21, 21, respectively. In this way, the excavator 1 cantravel forward and backward. In addition, the lower travel body 2 isprovided with a blade 23 and a blade cylinder 23 a that is a hydrauliccylinder for rotating the blade 23 in a vertical direction.

The work unit 3 includes a boom 31, an arm 32, and a bucket 33 andindependently drives these components to enable excavation work ofgravel or the like. The boom 31, the arm 32, and the bucket 33 eachcorrespond to a work section, and the excavator 1 has a plurality of thework sections.

The boom 31 has a base end portion that is supported by a front portionof the upper turning body 4, and is rotated by a boom cylinder 31 amovable in a freely extendable/contractable manner. The arm 32 has abase end portion that is supported by a tip portion of the boom 31, andis rotated by an arm cylinder 32 a movable in a freelyextendable/contractable manner. The bucket 33 has a base end portionthat is supported by a tip portion of the arm 32, and is rotated by abucket cylinder 33 a movable in a freely extendable/contractable manner.Each of the boom cylinder 31 a, the arm cylinder 32 a, and the bucketcylinder 33 a is constructed of a hydraulic cylinder.

The upper turning body 4 is configured to be turnable with respect tothe lower travel body 2 via a turning bearing (not illustrated). In theupper turning body 4, an operation section 41, a turn table 42, aturning motor 43, a battery 62, and the like are arranged. With drivepower of the turning motor 43 as a hydraulic motor, the upper turningbody 4 turns via the turning bearing (not illustrated). In addition,plural hydraulic pumps (not illustrated in FIG. 1) that are driven by anelectric motor are disposed in the upper turning body 4. These hydraulicpumps supply hydraulic oil to the hydraulic motors (the travel motors22L, 22R and the turning motor 43) and the hydraulic cylinders (theblade cylinder 23 a, the boom cylinder 31 a, the arm cylinder 32 a, andthe bucket cylinder 33 a). The hydraulic motors and the hydrauliccylinders will collectively be referred to as hydraulic actuators.

An operator seat 411 is arranged in the operation section 41. A left andright pair of work operation levers 412L, 412R is arranged on left andright sides of the operator seat 411, and a pair of travel levers 413L,413R is arranged in front of the operator seat 411. When seated on theoperator seat 411 and operating the work operation levers 412L, 412R,the travel levers 413L, 413R, or the like, an operator can control eachof the hydraulic actuators, which allows travel, turning, work, or thelike.

The work operation levers 412L, 412R are integrally attached to a leverstand 414. From this lever stand 414, a cut-off lever 415 for turningon/off an operation of the work unit 3 using the work operation levers412L, 412R extends forward. The cut-off lever 415 is configured to bevertically rotatable, and is configured to be brought into a state ofallowing actuation of the work unit 3 with operations of the workoperation levers 412L, 412R when being rotated downward and to bebrought into a locked state where the work unit 3 is not actuated evenwith the operations of the work operation levers 412L, 412R when beingrotated upward. In the lever stand 414, a cut-off switch 416 is providedto detect a rotation position of the cut-off lever 415. The cut-offswitch 416 is configured to be turned on when the cut-off lever 415 isrotated downward and to be turned off when the cut-off lever 415 isrotated upward.

The upper turning body 4 is provided with a power supply port, which isnot illustrated. When a power supply cable 51 for a commercial powersupply 5 (corresponding to the external power supply) is connected tothis power supply port, the commercial power supply 5 can be connectedto a power supply system 6, which will be described below.

The hydraulic pump that supplies the hydraulic oil to the hydraulicactuator is configured to be actuated by the electric motor that isdriven by electric power, and the commercial power supply 5 and thebattery 62 supply the electric power to the electric motor.

[Configuration of Hydraulic Circuit]

FIG. 3 illustrates a hydraulic circuit 100 that is mounted on theexcavator 1. The hydraulic circuit 100 includes a first actuator 111, asecond actuator 112, a hydraulic pump 113, a pilot pump 114, a firstdirection switching valve 115, a second direction switching valve 116,and an operation device 117.

The first actuator 111 is a hydraulic motor that is driven by thehydraulic oil supplied from the hydraulic pump 113. Examples of thefirst actuator 111 are the travel motors 22L, 22R. The second actuator112 is a hydraulic cylinder that is driven by the hydraulic oil suppliedfrom the hydraulic pump 113. An example of the second actuator 112 isthe boom cylinder 31 a.

The hydraulic pump 113 is driven by the electric motor, which is notillustrated, to discharge the hydraulic oil. The hydraulic oildischarged from the hydraulic pump 113 is supplied to the firstdirection switching valve 115 and the second direction switching valve116 via an oil passage 113 a and an oil passage 113 b. In FIG. 3, theoil passages for the hydraulic oil supplied from the hydraulic pump 113to the first actuator 111 and the second actuator 112 are indicated bysolid lines.

The first direction switching valve 115 is a direction switching valveof a pilot type capable of switching a direction of the hydraulic oilsupplied to the first actuator 111 and adjusting a flow rate thereof.The second direction switching valve 116 is a direction switching valveof the pilot type capable of switching a direction of the hydraulic oilsupplied to the second actuator 112 and adjusting a flow rate thereof.

The pilot pump 114 discharges pilot hydraulic oil as a command input tothe first direction switching valve 115 and the second directionswitching valve 116. In FIG. 3, oil passages for the pilot hydraulic oilsupplied from the pilot pump 114 to the second direction switching valve116 are indicated by broken lines (here, oil passages for the pilothydraulic oil supplied from the pilot pump 114 to the first directionswitching valve 115 are not illustrated). The pilot pump 114 generates apilot pressure to be applied to the first direction switching valve 115and the second direction switching valve 116. The pilot pump 114 isdriven by the electric motor, which is not illustrated, and dischargesthe hydraulic oil so as to generate the pilot pressure in an oil passage114 a.

The first direction switching valve 115 can be switched to any of pluralpositions by sliding a spool. In the case where the pilot pressure isapplied to none of a pilot port 115 a and a pilot port 115 b of thefirst direction switching valve 115, an urging force of a spring keepsthe first direction switching valve 115 at a neutral position. In thecase where the first direction switching valve 115 is at the neutralposition, the hydraulic oil is not supplied from the oil passage 113 bto the first actuator 111.

On the other hand, in the case where the pilot pressure is applied tothe pilot port 115 a or the pilot port 115 b of the first directionswitching valve 115, the first direction switching valve 115 is switchedfrom the neutral position to another position, and the hydraulic oil issupplied to the first actuator 111 via an oil passage 111 a or an oilpassage 111 b. With the hydraulic oil that is supplied via the oilpassage 111 a or the oil passage 111 b, the first actuator 111 isrotationally driven in a positive direction or a reverse direction.

The second direction switching valve 116 can be switched to any ofplural positions by sliding a spool. In the case where the pilotpressure is applied to none of a pilot port 116 a and a pilot port 116 bof the second direction switching valve 116, an urging force of a springkeeps the second direction switching valve 116 at a neutral position. Inthe case where the second direction switching valve 116 is at theneutral position, the hydraulic oil is not supplied from the oil passage113 a to the second actuator 112.

On the other hand, in the case where the pilot pressure is applied tothe pilot port 116 a or the pilot port 116 b of the second directionswitching valve 116, the second direction switching valve 116 isswitched from the neutral position to another position, and thehydraulic oil is supplied to the second actuator 112 via an oil passage112 a or an oil passage 112 b. With the hydraulic oil that is suppliedvia the oil passage 112 a or the oil passage 112 b, the second actuator112 is contracted.

The operation device 117 has a remote control valve 117 a for switchinga direction and the pressure of the pilot hydraulic oil to be suppliedto the second direction switching valve 116. Examples of the operationdevice 117 are the work operation levers 412L, 412R. The remote controlvalve 117 a is connected to the oil passage 114 a. The remote controlvalve 117 a is also connected to the pilot port 116 a and the pilot port116 b of the second direction switching valve 116 via an oil passage 117b and an oil passage 117 c, respectively. The remote control valve 117 asupplies, as the pilot hydraulic oil, the hydraulic oil that is suppliedfrom the pilot pump 114 via the oil passage 114 a to the seconddirection switching valve 116. When the operation device 117 isoperated, it is possible to switch the second direction switching valve116, to switch the direction of the hydraulic oil to be supplied to thesecond actuator 112, and to adjust the flow rate of such hydraulic oil.

An on/off valve 180 is provided in the oil passage 114 a between thepilot pump 114 and the remote control valve 117 a. The on/off valve 180is constructed of an electromagnetic valve and includes a solenoid 180a. The solenoid 180 a is connected to the cut-off switch 416. Asillustrated in FIG. 3, when the cut-off lever 415 is rotated downwardand turns on the cut-off switch 416, the solenoid 180 a is energized tobring the on/off valve 180 into a communication state. As a result, thehydraulic oil from the pilot pump 114 is supplied to the remote controlvalve 117 a via the on/off valve 180. On the other hand, as illustratedby two-dot chain lines in FIG. 3, when the cut-off lever 415 is rotatedupward, the cut-off switch 416 is turned off by an urging force of aspring, the solenoid 180 a is no longer energized, and the on/off valve180 is brought into a shutoff state by an urging force of a spring. Inthis way, the hydraulic oil from the pilot pump 114 is no longersupplied to the remote control valve 117 a, and the pilot pressure is nolonger applied to the second direction switching valve 116 even with theoperation of the operation device 117. As a result, the hydraulic oil isnot supplied to the second actuator 112, and an operation of the secondactuator 112 is restricted. That is, when being rotated downward, thecut-off lever 415 is brought into a state of allowing the actuation ofthe work unit 3 with the operation of the operation device 117. Whenbeing rotated upward, the cut-off lever 415 is brought into a lockedstate where the work unit 3 is not actuated even with the operation ofthe operation device 117.

[Configuration of Power Supply System]

A description will be made on the power supply system 6 that is mountedon the excavator 1 and supplies the electric power to the electric motor7 with reference to FIG. 4. The power supply system 6 includes: a powersupply 61 that converts an alternating-current power supply voltage ofthe commercial power supply 5 into a direct-current power supplyvoltage; a battery 62 that charges or discharges the electric power fromthe power supply 61; an inverter 63 that converts the direct-currentpower supply voltage into the alternating-current power supply voltage;a first electrical circuit 6 a that supplies the electric power from thepower supply 61 to the inverter 63; a second electrical circuit 6 b thatjoins the first electrical circuit 6 a from the battery 62; an inverterrelay 64 arranged between the inverter 63 and a junction point 6 cbetween the first electrical circuit 6 a and the second electricalcircuit 6 b; a battery relay 65 arranged between the junction point 6 cand the battery 62; and a power supply relay 66 arranged between thejunction point 6 c and the power supply 61.

The power supply 61 converts the alternating-current voltage that issupplied from the commercial power supply 5 via the power supply cable51 into the direct-current voltage. This direct-current voltage issupplied to the battery 62 via the power supply relay 66 and the batteryrelay 65, and the battery 62 is thereby charged. The direct-currentvoltage of the power supply 61 is also supplied to the inverter 63 viathe power supply relay 66 and the inverter relay 64.

The battery 62 supplies the direct-current voltage to the inverter 63via the battery relay 65 and the inverter relay 64. An example of thebattery 62 is a lithium-ion battery.

The inverter 63 converts the direct-current voltage, which is suppliedfrom the power supply 61 and/or the battery 62, into thealternating-current voltage. This alternating-current voltage issupplied to an electric motor 7. The electric motor 7 actuates thehydraulic pump 113. Although only the hydraulic pump 113 is illustratedin FIG. 4, the plural hydraulic pumps may be provided.

The power supply system 6 also includes a system controller 67 forcontrolling the power supply system 6. The system controller 67 executescontrol of the electric power to be supplied to the electric motor 7,control of charging of the battery 62, and the like. More specifically,the system controller 67 controls the power supply 61, the inverter 63,the inverter relay 64, the battery relay 65, the power supply relay 66,and the like so as to be able to drive the electric motor 7 and chargethe battery 62.

The power supply system 6 has plural power supply modes illustrated inFIG. 5A to FIG. 5D. As illustrated in FIG. 5A, the power supply system 6can have a commercial power supply mode, in which the electric power isonly supplied from the commercial power supply 5 to drive the electricmotor 7, by contacting contacts of the inverter relay 64 and the powersupply relay 66 and separating contacts of the battery relay 65. In thisway, a frequency of use of the battery 62 can be reduced, and life ofthe battery 62 can thereby be extended. In addition, even in the casewhere the battery 62 is brought into an abnormal state, the work can becontinued by using the commercial power supply 5 in the commercial powersupply mode.

As illustrated in FIG. 5B, the power supply system 6 can have a two-waymode (corresponding to the first power supply mode), in which theelectric power is supplied from the battery 62 and the commercial powersupply 5 to drive the electric motor 7, by contacting the three contactsof the inverter relay 64, the power supply relay 66, and the batteryrelay 65.

As illustrated in FIG. 5C, the power supply system 6 can have a batterymode (corresponding to the second power supply mode), in which theelectric power is only supplied from the battery 62 to drive theelectric motor 7, by contacting the contacts of the inverter relay 64and the battery relay 65 and separating the contact of the power supplyrelay 66.

As illustrated in FIG. 5D, the power supply system 6 can have a chargingmode, in which only the battery 62 is charged by using the commercialpower supply 5, by contacting the contacts of the battery relay 65 andthe power supply relay 66 and separating the contact of the inverterrelay 64.

Next, a description will be made on a control method for switching thepower supply mode described above. FIG. 6 is a flowchart illustrating aprocedure of switching control of the power supply mode. First, theoperator turns on the power supply. Next, the operator selects the powersupply mode by using a power supply mode selection switch. In step S1,it is determined which power supply mode is selected. In the case wherea mode 1 is selected, the system controller 67 turns on the inverterrelay 64 and the power supply relay 66 and turns off the battery relay65 so as to implement the commercial power supply mode.

Meanwhile, in the case where a mode 2 or a mode 3 is selected in stepS1, in next step S2, it is determined whether the power supply 61 can beused. The power supply 61 includes a control section that determineswhether the power supply 61 itself can be used and, if cannot be used,sends an error signal to the system controller 67. In the case where thesystem controller 67 receives the error signal from the power supply 61,the system controller 67 determines that the power supply 61 cannot beused.

If it is determined in step S2 that the power supply 61 “cannot beused”, in next step S3, it is determined whether the battery 62 can beused. The battery 62 includes a control section that determines whetherthe battery 62 itself can be used and, if cannot be used, sends an errorsignal to the system controller 67. In the case where the systemcontroller 67 receives the error signal from the battery 62, the systemcontroller 67 determines that the battery 62 cannot be used. If it isdetermined in step S3 that the battery 62 “cannot be used”, the systemcontroller 67 issues an error.

On the other hand, if it is determined in step S3 that the battery 62“can be used”, in next step S4, the system controller 67 turns on thebattery relay 65. Next, in step S5, it is determined whether theinverter 63 can be used. The inverter 63 includes a control section thatdetermines whether the inverter 63 itself can be used and, if cannot beused, sends an error signal to the system controller 67. In the casewhere the system controller 67 receives the error signal from theinverter 63, the system controller 67 determines that the inverter 63cannot be used. If it is determined in step S5 that the inverter 63“cannot be used”, the system controller 67 issues an error.

On the other hand, if it is determined in step S5 that the inverter 63“can be used”, in next step S6, the system controller 67 turns on theinverter relay 64. In this way, it is possible to implement the batterymode (the second power supply mode) in which the electric power issupplied only from the battery 62 to drive the electric motor 7.

If it is determined in step S2 that the power supply 61 “can be used”,in next step S7, it is determined whether the battery 62 can be used. Ifit is determined in step S7 that the battery 62 “cannot be used”, thesystem controller 67 issues the error. On the other hand, if it isdetermined in step S7 that the battery 62 “can be used”, in next stepS8, the system controller 67 turns on the battery relay 65.

Next, in step S9, it is determined which power supply mode is selected.If it is determined that the mode 3 is selected, in next step S10,connection of the power supply cable 51 is checked. When the powersupply cable 51 is connected to the power supply port, the power supply61 detects this and sends a connection signal to the system controller67. In the case where the system controller 67 receives the connectionsignal from the power supply 61, the system controller 67 determinesthat the power supply cable 51 is connected to the power supply port. Ifit is determined in step S10 that the power supply cable 51 is “notconnected”, the system controller 67 issues an error.

On the other hand, if it is determined in step S10 that the power supplycable 51 is “connected”, in next step S11, the power supply relay 66 isturned on. In this way, it is possible to implement the charging mode inwhich only the battery 62 is charged by using the commercial powersupply 5.

If it is determined in step S9 that the mode 2 is selected, in next stepS12, it is determined whether the inverter 63 can be used. If theinverter 63 cannot be used, the system controller 67 issues the error.On the other hand, if it is determined in step S12 that the inverter 63can be used, in next step S13, the system controller 67 turns on theinverter relay 64.

Next, in step S14, the connection of the power supply cable 51 ischecked. If it is determined in step S14 that the power supply cable 51is “not connected”, the battery mode (the second power supply mode), inwhich the electric power is supplied only from the battery 62 to drivethe electric motor 7, is implemented.

On the other hand, if it is determined in step S14 that the power supplycable 51 is “connected”, in next step S15, the power supply relay 66 isturned on. In this way, it is possible to implement the two-way mode(the first power supply mode) in which the electric power is suppliedfrom the battery 62 and the commercial power supply 5 to drive theelectric motor 7.

Next, a description will be made on a control method for switchingbetween the two-way mode and the battery mode with reference to FIG. 7.In a state of the battery mode, in step S16, the connection of the powersupply cable 51 is checked. If it is determined in step S16 that thepower supply cable 51 is “not connected”, the battery mode continues.

On the other hand, if it is determined in step S16 that the power supplycable 51 is “connected”, in next step S17, it is determined whether therotation of the electric motor 7 is stopped. The electric motor 7 isprovided with a position sensor. The inverter 63 receives information onthe position sensor from the electric motor 7, calculates a rotationalspeed of the electric motor 7, and sends information on the rotationalspeed of the electric motor 7 to the system controller 67. Based on theinformation on the rotational speed of the electric motor 7, which isreceived from the inverter 63, the system controller 67 can determinewhether the rotation of the electric motor 7 is stopped. If it isdetermined “NO” in step S17 that the rotation of the electric motor 7 isnot stopped, the battery mode continues.

On the other hand, if it is determined “YES” in step S17 that therotation of the electric motor 7 is stopped, in next step S18, the powersupply relay 66 is turned on. In this way, the battery mode can beswitched to the two-way mode.

Meanwhile, in the two-way mode, in step S19, the connection of the powersupply cable 51 is checked. If it is determined in step S19 that thepower supply cable 51 is “connected”, the two-way mode continues.

On the other hand, if it is determined in step S19 that the power supplycable 51 is “not connected”, in next step S20, the power supply relay 66is turned off. In this way, the two-way mode can be switched to thebattery mode.

Another Embodiment

As illustrated in FIG. 8, when the battery mode is switched to thetwo-way mode, in addition to checking of the connection of the powersupply cable 51 and checking of the stop of the rotation of the electricmotor 7, it may be determined whether the cut-off lever 415 is rotatedupward, and the operation of the hydraulic actuator is therebyrestricted. Based on information from the cut-off switch 416 on whetherthe cut-off lever 415 is rotated upward or downward, the systemcontroller 67 can determine whether the cut-off lever 415 is rotatedupward. If it is determined “YES” in step S17, in next step S21, it isdetermined whether the cut-off lever 415 is rotated upward. If it isdetermined “NO” in step S21 that the cut-off lever 415 is not rotateddownward, the battery mode continues. On the other hand, if it isdetermined “YES” that the cut-off lever 415 is rotated upward, in nextstep S18, the power supply relay 66 is turned on.

The description has been made so far on the embodiments of the presentinvention with reference to the drawings. However, it should beconsidered that the specific configuration is not limited to thatdescribed in each of these embodiments. The scope of the presentinvention is indicated not only by the description of the aboveembodiments but also by the claims and further includes allmodifications that fall within and are equivalent to the scope of theclaims.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 excavator    -   5 commercial power supply    -   51 power supply cable    -   6 power supply system    -   7 electric motor    -   62 battery    -   112 second actuator    -   113 hydraulic pump    -   415 cut-off lever

The invention claimed is:
 1. An electric work machine including: anelectric motor having an external power supply and a battery as drivepower sources; and a hydraulic actuator having, as a hydraulic pressuresource, a hydraulic pump driven by the electric motor, the electric workmachine comprising: a first power supply mode in which the electricmotor is driven while the battery is being charged by the external powersupply; and a second power supply mode in which the electric motor isdriven only by the battery, wherein: in the case where a power supplycable for supplying electric power from the external power supply isconnected to a power supply port and rotation of the electric motor isstopped, the second power supply mode is shifted to the first powersupply mode; and in the case where the power supply cable for supplyingthe electric power from the external power supply is connected to thepower supply port, where the rotation of the electric motor is stopped,and where a cut-off lever for restricting an operation of the hydraulicactuator is rotated upward by blocking a pilot pressure used to operatethe hydraulic actuator, so as to restrict the operation of the hydraulicactuator, the second power supply mode is shifted to the first powersupply mode.
 2. The electric work machine according to claim 1, whereinin the case where the power supply cable is disconnected from the powersupply port, the first power supply mode is shifted to the second powersupply mode.
 3. An electric work machine including: an electric motorconfigured to receive power from one or more drive power sources, theone or more drive power sources including an external power supply and abattery as drive power sources; a hydraulic actuator having, as ahydraulic pressure source, a hydraulic pump configured to be driven bythe electric motor; and a power supply port configured toconnect/disconnect with a power supply cable; wherein: the electric workmachine is configured to operate in: a first power supply mode in whichthe electric motor is driven while the battery is being charged by theexternal power supply; and a second power supply mode in which theelectric motor is driven only by the battery, and in the case where thepower supply cable for supplying electric power from the external powersupply is connected to the power supply port and rotation of theelectric motor is stopped, the second power supply mode is shifted tothe first power supply mode.
 4. The electric work machine according toclaim 3, wherein the external power supply includes a commercial powersupply, and wherein the power supply port is configured to receive powerfrom the external power supply via the power supply cable.
 5. Theelectric work machine according to claim 3, wherein, in the case wherethe power supply cable is connected to the power supply port, the powersupply port is configured to receive alternating-current (AC) power fromthe external power supply via the power supply cable.
 6. The electricwork machine according to claim 3, wherein in the case where the powersupply cable for supplying the electric power from the external powersupply is connected to the power supply port, where the rotation of theelectric motor is stopped, and where a cut-off lever for restricting anoperation of the hydraulic actuator is rotated upward by blocking apilot pressure used to operate the hydraulic actuator, so as to restrictthe operation of the hydraulic actuator, the second power supply mode isshifted to the first power supply mode.
 7. The electric work machineaccording to claim 3, wherein in the case where the power supply cableis disconnected from the power supply port, the first power supply modeis shifted to the second power supply mode.
 8. An electric work machineincluding: an electric motor configured to receive power from one ormore drive power sources, the one or more drive power sources includingan external power supply and a battery as drive power sources; and apower supply port configured to connect/disconnect with a power supplycable and configured to receive power from the external power supply viathe power supply cable; wherein: the electric work machine is configuredto operate in: a first power supply mode in which the electric motor isdriven while the battery is being charged by the external power supply;and a second power supply mode in which the electric motor is drivenonly by the battery, in the case where the power supply cable forsupplying electric power from the external power supply is connected tothe power supply port and rotation of the electric motor is stopped, thesecond power supply mode is shifted to the first power supply mode, andin the case where the power supply cable is disconnected from the powersupply port, the first power supply mode is shifted to the second powersupply mode.
 9. The electric work machine according to claim 8, whereinthe external power supply includes a commercial power supply.
 10. Theelectric work machine according to claim 8, wherein, in the case wherethe power supply cable is connected to the power supply port, the powersupply port is configured to receive alternating-current (AC) power fromthe external power supply via the power supply cable.
 11. The electricwork machine according to claim 8, further comprising a hydraulicactuator having, as a hydraulic pressure source, a hydraulic pumpconfigured to be driven by the electric motor.
 12. The electric workmachine according to claim 8, wherein, in the case where the powersupply cable for supplying the electric power from the external powersupply is connected to the power supply port, where the rotation of theelectric motor is stopped, and where a cut-off lever for restricting anoperation of a hydraulic actuator is rotated upward by blocking a pilotpressure used to operate the hydraulic actuator, so as to restrict theoperation of the hydraulic actuator, the second power supply mode isshifted to the first power supply mode.
 13. The electric work machineaccording to claim 8, further comprising a hydraulic pump configured tobe driven by the electric motor, the hydraulic pump associated with ahydraulic actuator.